/*
 * Copyright (C) 2011 Markus Junginger, greenrobot (http://greenrobot.de)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.mlizhi.base.dao.internal;

import java.util.Arrays;

import com.mlizhi.base.dao.DaoLog;

/**
 * An minimalistic hash map optimized for long keys.
 * 
 * @author Markus
 * 
 * @param <T>
 *The class to store.
 */
public final class LongHashMap<T> {
final static class Entry<T> {
final long key;
T value;
Entry<T> next;

Entry(long key, T value, Entry<T> next) {
this.key = key;
this.value = value;
this.next = next;
}
}

private Entry<T>[] table;
private int capacity;
private int threshold;
private int size;

public LongHashMap() {
this(16);
}

@SuppressWarnings("unchecked")
public LongHashMap(int capacity) {
this.capacity = capacity;
this.threshold = capacity * 4 / 3;
this.table = new Entry[capacity];
}

public boolean containsKey(long key) {
final int index = ((((int) (key >>> 32)) ^ ((int) (key))) & 0x7fffffff) % capacity;

for (Entry<T> entry = table[index]; entry != null; entry = entry.next) {
if (entry.key == key) {
return true;
}
}
return false;
}

public T get(long key) {
final int index = ((((int) (key >>> 32)) ^ ((int) (key))) & 0x7fffffff) % capacity;
for (Entry<T> entry = table[index]; entry != null; entry = entry.next) {
if (entry.key == key) {
return entry.value;
}
}
return null;
}

public T put(long key, T value) {
final int index = ((((int) (key >>> 32)) ^ ((int) (key))) & 0x7fffffff) % capacity;
final Entry<T> entryOriginal = table[index];
for (Entry<T> entry = entryOriginal; entry != null; entry = entry.next) {
if (entry.key == key) {
T oldValue = entry.value;
entry.value = value;
return oldValue;
}
}
table[index] = new Entry<T>(key, value, entryOriginal);
size++;
if (size > threshold) {
setCapacity(2 * capacity);
}
return null;
}

public T remove(long key) {
int index = ((((int) (key >>> 32)) ^ ((int) (key))) & 0x7fffffff) % capacity;
Entry<T> previous = null;
Entry<T> entry = table[index];
while (entry != null) {
Entry<T> next = entry.next;
if (entry.key == key) {
if (previous == null) {
table[index] = next;
} else {
previous.next = next;
}
size--;
return entry.value;
}
previous = entry;
entry = next;
}
return null;
}

public void clear() {
size = 0;
Arrays.fill(table, null);
}

public int size() {
return size;
}

public void setCapacity(int newCapacity) {
@SuppressWarnings("unchecked")
Entry<T>[] newTable = new Entry[newCapacity];
int length = table.length;
for (int i = 0; i < length; i++) {
Entry<T> entry = table[i];
while (entry != null) {
long key = entry.key;
int index = ((((int) (key >>> 32)) ^ ((int) (key))) & 0x7fffffff) % newCapacity;

Entry<T> originalNext = entry.next;
entry.next = newTable[index];
newTable[index] = entry;
entry = originalNext;
}
}
table = newTable;
capacity = newCapacity;
threshold = newCapacity * 4 / 3;
}

/** Target load: 0,6 */
public void reserveRoom(int entryCount) {
setCapacity(entryCount * 5 / 3);
}

public void logStats() {
int collisions = 0;
for (Entry<T> entry : table) {
while (entry != null && entry.next != null) {
collisions++;
entry = entry.next;
}
}
DaoLog.d("load: " + ((float) size) / capacity + ", size: " + size + ", capa: " + capacity + ", collisions: "
+ collisions + ", collision ratio: " + ((float) collisions) / size);
}

}
